Some nice analysis Dr Pete there - My authorship got whacked in the update and have been trying to find patterns in why. I think you are right, Google is using some superficial signals that we don't have a full understanding of it yet. In my case, it looks like site authority is an issue as an established author's post on my site also got hit, but didn't on other more established sites. My authorship still shows in SERPs for some site's I have written for. However, my authorship also got hit for an established site when authors on the same site did not indicating that author trust is also a factor. I wrote an article about it on my blog http://www.colindocherty.co.uk/blog/google-authorship-picture-disappeared